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The research on enhancing the toughness and improving the density of silicon carbide ceramics has been our ongoing work. The main methods for enhancing the toughness of silicon carbide ceramics are to change the composition of the ceramic material, such as by increasing fiber/whisker toughening, second phase particle toughening, and changing the ceramic forming process to change the internal microstructure of the ceramic.

In the early days, armor plates were made of homogeneous armor, and most tanks and other armored vehicles were covered with steel plates. However, the density and weight of steel plate materials were high, and thick armor relatively reduced mobility. Therefore, in order to improve combat capabilities on the battlefield, after the end of World War II, specialized armor forms appeared by coating a layer of ceramic or depleted uranium on steel armor. Although the characteristics of ceramic materials were discovered early, their actual application for military purposes was not long.

1.Application of silicon carbide ceramic film in high-temperature flue gas purification Silicon carbide ceramic film has unique advantages in the field of high-temperature flue gas treatment due to its high temperature resistance, corrosion resistance, and thermal shock resistance. For particulate pollutants such as PM2.5, the dust removal mechanism of silicon carbide ceramic membrane is pore screening, interception, adsorption, etc. In addition, silicon carbide film has been widely used in high-temperature dust removal industries such as coal chemical, polycrystalline silicon, and steel.

Silicon carbide bulletproof ceramic Silicon carbide has extremely strong covalent bonds and maintains high strength even at high temperatures. This structural characteristic endows silicon carbide ceramics with excellent strength, high hardness, wear resistance, corrosion resistance, high thermal conductivity, and good thermal shock resistance; At the same time, silicon carbide ceramics have a moderate price and high cost-effectiveness, making them one of the most promising high-performance armor and protective materials.

In the military industry, pressureless sintered silicon carbide shines like a brilliant star. As a new type of material, it not only has advantages such as high hardness and thermal conductivity, but also can withstand high temperature and high pressure in extreme environments, making it an important component of military equipment. The emergence of pressureless sintered silicon carbide has brought new possibilities for the development of military technology, significantly enhancing the strategic advantages of military equipment. Its widespread application has injected new vitality into the military industry, elevating military strength to a new height.

Hot isostatic pressing sintering Hot isostatic pressing sintering of boron carbide involves placing powder compacts or encapsulated powders into high-pressure containers. Inert gases (such as N2 and Ar) can be used as pressure transfer media without the need for sintering aids, subjecting the powders to isotropic pressure and reducing sintering temperature. This results in the production of boron carbide ceramic materials with fine crystal microstructure, high bending strength, and density. Hot isostatic pressing sintering is a simple and low-cost preparation technology that can produce high-density, high-strength, and uniformly distributed grain products. This technology can achieve one-time molding of structurally complex products. The disadvantage is that the equipment investment is large and the equipment price is expensive.

Sintering is a crucial step in the preparation of B4C ceramics, and the main factors affecting the sintering of B4C ceramics include sintering method, particle size and activity of powder raw materials, type and dosage of additives, sintering temperature and insulation time, etc. At present, the sintering methods for boron carbide ceramic powder mainly include pressureless sintering, hot pressing sintering, hot isostatic pressing sintering, discharge plasma sintering, etc.Now let's talk about the advantages and disadvantages of pressureless sintering and hot pressing sintering.

Boron carbide has a history of nearly 170 years of development, and its atomic structure has been widely studied in recent years. Its main crystal structure is a 12 atom icosahedron and a three atom chain connected to the icosahedron. This structure is also known as a hexagonal structure, where carbon atoms and boron atoms can replace each other, resulting in boron carbide having many isomers.

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Boron carbide has a complex crystal structure, which is a characteristic of borides centered on the pentahedron. The B12 octahedron forms a rhombic lattice unit around the C-B-C chain at the center of the unit cell (space group: R3m, lattice constant: a=0.56 nm and c=1.212 nm), and all carbon atoms bridge adjacent three octahedra. The B12 octahedron and bridging carbon form a network plane parallel to the c-plane, which is stacked along the c-axis to form a layered structure. The two basic structural units of a lattice are the B12 octahedron and the B6 octahedron. Due to the small size of the B6 octahedron, it cannot be combined. On the contrary, they bind to the adjacent B12 octahedra, which weakens the bonding of the c-plane.

After sintering with a mixture of coarse and fine powders, the bonding of SiC ceramic particles is smaller and tighter compared to single powder sintering. Due to the moderate difference in particle size between the coarse and fine powders used, the fine particles can better fill the pores between the coarse particles. Therefore, after sintering, the grain size is more consistent, and the distribution of carbon and pores is more uniform, without obvious aggregation or abnormal grain growth.

1. Application of boron carbide in nuclear industry Boron carbide has a high neutron absorption cross-section and a wide energy spectrum for absorbing neutrons, and is commonly used as a neutron absorption material in nuclear reactors. The thermal cross-section of the boron 10 isotope is as high as 347 × 10-24cm2, second only to a few elements such as gadolinium, samarium, and cadmium, making it an efficient thermal neutron absorber. In addition, boron carbide is rich in resources, corrosion-resistant, has good thermal stability, does not produce radioactive isotopes, and has low secondary radiation energy. Therefore, boron carbide is widely used as a control material and shielding material in nuclear reactors.